We hear lots about Paul (Saul) in the bible and most of it is in light of all the good things he was teaching and preaching, all the people he brought to Christ and the persecution he faced. But there are a few excerpts of how evil he was prior to becoming a Christian. He stood by while Stephen was stoned here in Acts and it says "Saul was there, giving approval to his (Stephen's) death."
Acts 9: 1 says "Meanwhile, Saul was uttering threats with every breath and was eager to kill the Lord’s followers." He really was not a nice person.
And yet look at all the great things he did in Christ's name throughout the rest of his life.
We need to try to remember that although people may have done very bad things in their lives there is always hope for redemption and God can use a "bad" person in mighty, mighty ways.